The invention provides a flashlight activated in response to a power failure or an alarm produced by a smoke detector so that a person in a dark and/or smoke-filled or smoke-filling room can use the light to escape. Flashlights activated by an audible smoke detector alarm are known. For example, U.S. Pat. No. 4,432,041 describes a flashlight powered entirely by internal batteries and retained by a holster mounted on a wall. The flashlight responds to a smoke detector alarm by turning on the light. The flashlight includes a spring activated switch. When the flashlight is withdrawn from the holster, a retaining force on a plug within the flashlight is released so the plug is ejected, closing a switch, and the flashlight remains illuminated. In the absence of removal of the flashlight from the holster, the light is extinguished automatically after a delay following termination of the smoke detector alarm. The lamp of this flashlight and the alarm detection circuitry of this flashlight are powered solely by internal batteries that are gradually consumed in operating the audible alarm detector while listening for a smoke detector alarm. Therefore, the flashlight described in U.S. Pat. No. 4,432,041 includes a low voltage detector for warning the user that the batteries have declined sufficiently in power to require replacement.
It is desirable in a flashlight activated by an audible smoke detector alarm to provide a long-life power source. Preferably, batteries are employed so that the flashlight is portable. To extend the lifetime of the batteries to the shelf life of the batteries, it is desired that the batteries not be drained during times when the flashlight is not illuminated.